THE GENUS ANASPIDES. 801 



In the first place, Acantliotelson and the doubtfully distinct Belotelson, are made to 

 constitute a sub-order Syncarida " standing near or at the base of the Thoracostraca, 

 not far from the Stomapoda and Schizopoda, and with appendages closely homologous 

 with those of these two groups." We find it difficult to see how such an homology 

 could be simultaneously close with the limbs both of Schizopod and Stomatopod. Under 

 the name Gampsonychidse Packard unites the genera Palseocaris and Gampsonyx, 

 ranking them as a family of the Schizopoda. The reasons for this marked difference in 

 the systematic rank assigned to these two groups are not very clear, for while Packard 

 enumerates the resemblances between the Syncarida and the Gampsonychidse, he 

 nowhere indicates what he considers as the essential distinctions between the two.* 

 As a matter of fact, Acantliotelson approaches very closely indeed to Gampsonyx ; so 

 far as we can gather, the only fundamental difference between the two lies in the fact 

 that the thoracic limbs of Acantliotelson are stated not to possess exopods. In view, 

 however, of the uncertain indications of these organs in Gampsonyx and in Palseocaris 

 it seems hardly safe to lay too much stress on their alleged absence from Acantliotelson. 

 By other palaeontologists the genera in question have been generally referred, on account 

 of the absence of a carapace, to the EdriopJithalmata. Gampsonyx is described by 

 Jordan and v. Meyer as an Amphipod with characters of the Decapoda, particularly 

 of the Macrura, while Acantliotelson was placed by its discoverers among the Isopoda t 

 and these views have been recently endorsed, though with an expression of doubt, 

 by so high an authority as Dr Henry WooDWARD.t 



We find, then, that Anaspides agrees with the extinct genera above enumerated in 

 the essential point in which they have hitherto stood alone : the combination of Podoph- 

 thalmate characters with a completely segmented body and the lack of a carapace. 

 We have seen that some at least — probably all — of these genera show characters of 

 the Schizopoda, to which group Anaspides is most closely allied. We find probable 

 agreement in such points as the apparent division of the head region into two seg- 

 ments as by the " cervical groove " in Anaspides. Such differences as have appeared 

 are readily explicable as comparatively unimportant differentiations which might be 

 expected to occur within the limits of the group, or as due to the present imperfect state 

 of our knowledge of the fossil forms. We conclude, therefore, that Anaspides is to be 

 regarded as the representative of a group of primitive Malacostraca, which had already, 

 in Palaeozoic times, attained a certain degree of specialisation and a very wide distribu- 

 tion. 



* Apparently, however, Packard's views on this point have been somewhat modified, for in the 5th edition of 

 his text-book of Zoology, published in the same year (1886) as the papers above referred to he uses the term Syncarida 

 as including all the genera above named. 



t " Anniversary Address," Proc. Geol. Soc, lii., 1896. 



